1. Core heat treatment method: Normalization
Treatment process: Heat the steel to a temperature above the Ac3 critical point (usually 880–920°C), hold it for a certain period to ensure uniform heating, then cool it in air.
Performance improvement: Refines the grain structure of the steel, making the microstructure more uniform. This directly enhances toughness (reducing brittleness) and slightly improves yield strength and tensile strength, while maintaining good formability.
2. Improvement in corrosion resistance
Mechanism: Reasonable heat treatment (e.g., precise control of cooling rate during normalization) optimizes the distribution and morphology of alloying elements (such as Cu, Cr, Ni) in Q355GNH.
Effect: Promotes the formation of a dense, stable oxide film on the steel surface. This oxide film acts as a barrier to prevent further corrosion by the external environment, thereby enhancing long-term weathering corrosion resistance.
3. Optimization of processing performance
Impact on processing: Heat treatment reduces internal stress in the steel (generated during rolling or forming). It also softens overly hard microstructures caused by improper rolling.
Practical value: Improves the steel's machinability (e.g., reducing tool wear during cutting) and weldability (reducing the risk of cracks during welding), making it easier to process into structural parts.
